Takeaways from IPCC’s Sixth Assessment Report for Transportation

On March 20, 2023, the Intergovernmental Panel on Climate Change (IPCC) provided a major update on the state of climate science and ways forward in its synthesis of the Sixth Assessment Report (AR6).

Here’s what the world’s top authority on climate says about climate action and transportation:

#1. Climate change is probably humankind’s biggest unfolding catastrophe.1 It multiplies the most problematic existing societal challenges and it exacerbates inequalities. Pretty much no one is left unscathed.

#2. We can head off continued warming and prepare for the unavoidable by making major coordinated commitments–which is manageable.2

#3. In fact, climate action is an opportunity for abundance.3 The solutions called for are largely centered in creating more inclusive, affordable, healthy, and joyous communities that make people better off. Sustainable and equitable development worth doing even without the benefits of decarbonization. 

#4. Rising to the challenge means rapid, broad, and deep decarbonization of our energy supply plus five principal “demand-side” areas: Food, buildings, industry, electrification, and land transportation.4 Emissions in all areas need to rapidly peak, decline, and move to nearly zero by 2050-2070.

#5. Decarbonization of transportation needs to include three major transformations:

  • Energy-Efficient Mobility Systems:5 Improving per-passenger energy productivity through development of systems to prioritize the widespread use of transit and other shared vehicles, vehicles right-sized for their purpose, and active transportation (e.g. bicycling and walking), meanwhile decreasing the distance between where people and things need to travel. Methods include safe streets for people outside of vehicles, more advanced public and community-based shared transportation, redesign of transportation for accessibility rather than car flow, inclusive housing, and inclusive use of public spaces. 
  • Resource-Efficient Electrification:6 Electrifying nearly every vehicle with wheels and a motor, while stewarding resources to create the most decarbonization for the materials employed. Methods include switching internal combustion engines with electric powertrains of existing vehicles in every class (e.g. cars, buses, and trucks), using the superior technology of battery-electric systems to advance new classes of highly-efficient small vehicles in urban areas (e.g. scooters and neighborhood electric vehicles), and creating new capabilities for active transportation (e.g. e-bikes). 
  • Rigorous Demand Management:7 Creating economic incentives to reward climate-compatible travel and contain the impact of vehicles and behaviors that are in conflict with decarbonization. Methods include programs of incentives for users making everyday travel choices and capital purchases (e.g. expanded use of transportation demand management or “TDM” initiatives), structural reforms (e.g. reorganizing subsidies to move beyond car-centric planning to interoperable multimodal systems, as well as ensuring public agencies have sufficient capacity and resources to conduct such work), and new creativity in public engagement (e.g., entrepreneurship to enhance user experiences, communication, and education).

#6. Everyone has a job to do.8 Climate action around transportation requires comprehensive support for activities as varied as public policy design, advocacy, organizing, technology deployment, education, applied research, and more. Those who have influence over urban areas and financial investments taking place are especially important. Leadership is contagious.

#7. Everything we can still do matters.9 Each increment of warming avoided can make an enormous difference.


1  From the IPCC’s published Headline Statements (Headlines), Summary for Policymakers (SPM), and Longer Report (LR). As of March 22, the full volume has not yet been published. Additional detail is available in the three reports the synthesis is based on, especially the 2022 report on Mitigation.

2  Climate change is a threat to human well-being and planetary health. (Headlines C.1). Climate change has reduced food security and affected water security, hindering efforts to meet Sustainable Development Goals (SPM A.2.4). Continued emissions will further affect all major climate system components, and many changes will be irreversible on centennial to millennial time scales and become larger with increasing global warming. Without urgent, effective, and equitable mitigation and adaptation actions, climate change increasingly threatens ecosystems, biodiversity, and the livelihoods, health and wellbeing of current and future generations. (C.1.3)

3 There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all. (Headlines C.1) All global modelled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot, and those that limit warming to 2°C (>67%), involve rapid and deep and, in most cases, immediate greenhouse gas emissions reductions in all sectors this decade. (SPM B.6). Low-cost decarbonization opportunities abound. (SPM Figure SPM.7.a)

4  Negative decarbonization opportunities abound. (SPM Figure SPM.7.a). Deep, rapid and sustained mitigation and accelerated implementation of adaptation actions in this decade would reduce projected losses and damages for humans and ecosystems (very high confidence), and deliver many co-benefits, especially for air quality and health (C.2) Mitigation options often have synergies with other aspects of sustainable development, but some options can also have trade-offs. There are potential synergies between sustainable development and, for instance, energy efficiency and renewable energy. Similarly, depending on the context, biological CDR methods like reforestation, improved forest management, soil carbon sequestration, peatland restoration and coastal blue carbon management can enhance biodiversity and ecosystem functions, employment and local livelihoods. However, afforestation or production of biomass crops can have adverse socio-economic and environmental impacts, including on biodiversity, food and water security, local livelihoods and the rights of Indigenous Peoples, especially if implemented at large scales and where land tenure is insecure. Modeled pathways that assume using resources more efficiently or that shift global development towards sustainability include fewer challenges, such as less dependence on CDR and pressure on land and biodiversity (B.6.4)

5  Rapid and far-reaching transitions across all sectors and systems are necessary to achieve deep and sustained emissions reductions and secure a liveable and sustainable future for all. (Headlines C.3) All global modeled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot, and those that limit warming to 2°C (>67%), involve rapid and deep and, in most cases, immediate greenhouse gas emissions reductions in all sectors this decade. Global net zero CO2 emissions are reached for these pathway categories, in the early 2050s and around the early 2070s, respectively. (Headlines B.6)

6 SPM Figure SPM.7.a

7 Urban systems are critical for achieving deep emissions reductions and advancing climate resilient development. Key adaptation and mitigation elements in cities include considering climate change impacts and risks (e.g. through climate services) in the design and planning of settlements and infrastructure; land use planning to achieve compact urban form, co-location of jobs and housing; supporting public transport and active mobility. (SPM C.3.4) Public transportation with bikes and rightsizing motor vehicles are among top 20 key modeled areas of mitigation, and the 5th (nearly tied with 4th) and 3rd-highest sources of mitigation that are cost-negative. (SPM Figure SPM.7.b) Urban systems are critical for achieving deep emissions reductions and advancing climate resilient development, particularly when this involves integrated planning that incorporates physical, natural and social infrastructure (high confidence). Deep emissions reductions and integrated adaptation actions are advanced by: integrated, inclusive land use planning and decision-making; compact urban form by co-locating jobs and housing; reducing or changing urban energy and material consumption; electrification in combination with low emissions sources; improved water and waste management infrastructure; and enhancing carbon uptake and storage in the urban environment (LR 4.5.3)

8 Electric vehicles powered by low-GHG emissions electricity have large potential to reduce land-based transport…The environmental footprint of battery production and growing concerns about critical minerals can be addressed by material and supply diversification strategies, energy and material efficiency improvements, and circular material flows. (SPM C.3.3)

9 Reducing industry GHG emissions entails coordinated action throughout value chains to promote all mitigation options, including demand management, energy and materials efficiency, circular material flows, as well as abatement technologies and transformational changes in production processes. (SPM C.3.3) The systemic change required to achieve rapid and deep emissions reductions and transformative adaptation to climate change is unprecedented in terms of scale, but not necessarily in terms of speed. Systems transitions include: deployment of low- or zero-emission technologies; reducing and changing demand through infrastructure design and access, socio-cultural and behavioral changes, and increased technological efficiency and adoption; social protection, climate services or other services; and protecting and restoring ecosystems. Feasible, effective, and low-cost options for mitigation and adaptation are already available. (SPM C.3.1) Electrification load brings significant new impacts that need to be reduced (SPM Figure SPM.7.b) Transport-related GHG emissions can be reduced by demand-side options and low-GHG emissions technologies. Changes in urban form, reallocation of street space for cycling and walking, digitalisation (e.g., teleworking) and programs that encourage changes in consumer behavior (e.g. transport, pricing) can reduce demand for transport services and support the shift to more energy efficient transport modes. (LR 4.5.3) Approaches that align goals and actions across sectors provide opportunities for multiple and large-scale benefits and avoided damages in the near-term. Such measures can also achieve greater benefits through cascading effects across sectors (medium confidence). For example, the feasibility of using land for both agriculture and centralized solar production can increase when such options are combined (high confidence). Similarly, integrated transport and energy infrastructure planning and operations can together reduce the environmental, social, and economic impacts of decarbonizing the transport and energy sectors (high confidence). (4.9) 

10 Urban systems are critical for achieving deep emissions reductions and advancing climate resilient development.  SPM (C.3.4) Finance, technology and international cooperation are critical enablers for accelerated climate action. (SPM C.7) 

11  There are gaps between projected emissions from implemented policies and those from NDCs and finance flows fall short of the levels needed to meet climate goals across all sectors and regions. (Headlines A.4). Every increment of global warming will intensify multiple and concurrent hazards. (Headlines B.1)

12  Climate change is a threat to human well-being and planetary health. There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all. Climate resilient development integrates adaptation and mitigation to advance sustainable development for all, and is enabled by increased international cooperation including improved access to adequate financial resources, particularly for vulnerable regions, sectors and groups, and inclusive governance and coordinated policies. The choices and actions implemented in this decade will have impacts now and for thousands of years (SMP C.1). Delayed mitigation and adaptation action would lock-in high-emissions infrastructure, raise risks of stranded assets and cost-escalation, reduce feasibility, and increase losses and damages (high confidence). Near-term actions involve high up-front investments and potentially disruptive changes that can be lessened by a range of enabling policies. (C.2)

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